Many atheletes and non-athletes utilize weight lifting or weight training exercises to build strength and/or bulk, to prevent injury, or to improve overall condition and appearance. Typically, weight training exercises are performed with either exercise machines or free weights, i.e., barbells and weighted plates, dumbbells, etc. For various reasons, most exercise programs incorporate both machines and free weights in a variety of different exercise routines to maximize the effect of working out a desired number of muscle groups.
One exercise maneuver that is frequently performed on an exercise machine is referred to as a leg extension. The leg extension exercise involves extending, against a pivotal weight resistance, one leg or both legs forwardly and outwardly from a flexed position to an extended position. The exercise is performed from a seated position, and the applied force of the legs is directed against pads connected to pivotal levers. Removable weights, or a stationary stack of weights are connectable to the lever to provide a selectable weight resistance.
There are presently a number of different machines available for performing a leg extension exercise. Some leg extension machines simply utilize a lever pivotally connected to a frame which includes a horizontal support, with removable weights supported on the lever. While relatively simple in construction, these machines are rather awkward for the exerciser because the horizontal support does not provide good leverage during the leg extension motion. Moreover, the support must remain substantially flat because these machines are generally also used for performing a leg curl exercise from a prone, face-down position.
Other leg extension exercise machines utilize a pulley and cable to couple the exercise movement to the weight resistance. At least one leg extension machine uses an eccentric cam and chain mechanism for the same purpose. Leg extension machines which utilize a cable/chain linkage require periodic maintenance to prevent friction buildup, which would otherwise result in an undesired increase in resistance to extension of the legs. Moreover, these additional parts also may wear out or function improperly and thus necessitate removal and repair.
Perhaps more importantly, these other leg extension machines do not always feel right or "fit" the body properly. For instance, structural components such as the pivot point or the lever length seem to be sized disproportionately for a large number of athletes. While some portion of this awkwardness may be attributable to the fact that most exercise machines are sized or shaped for an "average" size person and many people who use these machines are simply not of "average" musculoskeletal structure, there is also another degree of awkwardness which does not seem to be size-related at all. This latter degree of awkwardness relates to unnatural musculo-skeletal positioning that results directly from the orientation of the machine itself, even for an average size individual. As a result, muscles, bones and/or joints are subjected to unnecessary shear or compression stress during exercise with these machines. This disadvantage is particularly unfortunate in the case of the leg extension exercise because the leg extension is considered critical to minimizing the risk of injury to the knee joint, one of the body's most susceptible joints.
Finally, if the knee is injured, it is considered important to perform the leg extension exercise with one leg only during rehabilitation to allow close monitoring of progress. Unfortunately, single leg performance of a leg extension exercise on most of these machines seems to accentuate the awkwardness or uncomfortable fit of the machine.
It is therefore an object of the invention to provide a leg extension exercise machine that maximizes the exercise benefit attainable during a leg extension maneuver while minimizing skeletal or joint stress associated therewith.
It is another object of the invention to provide a leg extension exercise machine that reduces or eliminates the unnatural feel that seems to be inherent with other leg extension exercise machines.
It is still another object of th invention to provide a leg extension exercise machine which is particularly suitable for exercising one leg at a time.